Non-spherical cupreous powder



United States Patent 3,128,172 NON-SPHERECAL CUPREOUS POWDER Irwin D.Wagner and Luther D. Fetterolf, Palmerton, Pa., asslgnors to The NewJersey Zine Company, New York, N.Y., a corporation of New Jersey NoDrawing. Filed Dec. 27, 1960, Ser. No. 78,289 1 Claim. (Cl. 75-.5)

This invention relates to metallic copper powder and, more particularly,to a non-spherical copper powder which is particularly suitable forpowder metallurgical usage and to the method of making thisnon-spherical powder.

When metallic copper is atomized by presently known procedures, theresulting particles of copper powder are characteristically spherical inshape. Although a spherical powder can be packed more densely than anonspherical powder, a spherical powder cannot be effectively formedinto a compact.

We have now found that the characteristic shape of atomized copperparticles can be altered by incorporating between 2.5% and 49% by weightof cobalt in the copper prior to its atomization. The resulting cupreousmetal, when atomized with air, has a particle shape which is distinctlynon-spherical. Thus, the method of the present invention comprisesforming a molten copper-base alloy composed essentially of copper andfrom 2.5 to 49% cobalt, and thereafter atomizing the resulting moltencoppercobalt alloy with air. The resulting product is a powder ofnon-spherical cupreous particles consisting essentially of a copper-basealloy containing from 2.5 to 49% by weight of cobalt and the balancecopper.

The amount of cobalt which is useful in practicing the invention isprescribed by the fact that amounts less than 2.5% by weight of thecopper are not eliective in changing the characteristic spherical shapeof the copper particles, whereas the upper limit of 49% cobaltcorresponds to an amount which raises the melting (and hence thesintering) temperature of the alloy to the maximum value compatible withpractical operating procedure. Within this range, amounts of cobaltbetween 2.5% and about 4.5% by weight of the copper produce the desiredirregularly shaped particles of the cupreous alloy having a desirablylow sintering temperature.

The method of preparing the alloy and of producing the non-sphericalparticles of this alloy is illustrated by the following procedure whichwas used to produce powders of copper-cobalt alloys within and withoutthe effective range set forth hereinbefore. In each instance, metalliccopper was melted in a clay-graphite crucible and Was heated to atemperature well above its melting point while maintaining a protectivepowdered charcoal cover over the molten metal. The cobalt was added tothe molten copper and the melt was stirred Wtih a green stick in themanner of the poling process of the copper refining industry. After theresulting melt had been held in the crusible for about minutes to insurehomogeneity, it

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was atomized in conventional apparatus at a metal flow rate of 3 to 5pounds per minute and with the use of compressed air at to psi pressureFor each composition, tests were made to determine the particle shape ofthe powder, its apparent density and the weight loss of a compact madeunder a compacting pressure of 30 t.s.i. and tested according to theMetal Powder Industries Federation MPI Standard 15 for Determination ofGreen Strength of Compacted Metal Powder Specimens (a procedure in whichthe green compact is tumbled in a screen cage). The resulting test dataare summarized in the following table:

It will be readily seen from the foregoing data that air atomization ofcopper containing less than about 2.5% cobalt produces sphericalparticles that, because of this shape, cannot be compacted and thatcopper containing at least 2.5% cobalt produces, by air atomization,particles which are so irregular in shape that they form strong greencompacts.

We claim:

A copper-cobalt alloy powder having a composition consisting essentiallyof from about 2.5 to about 4.5 percent by weight of cobalt and theremainder essentially copper, the powder having been produced by forminga molten copper-cobalt alloy of said composition and thereafteratomizing the molten copper-cobalt alloy with air.

References Cited in the file of this patent UNITED STATES PATENTS1,834,687 Davis Dec. 1, 1931 1,957,214 Horstkatte May 1, 1934 2,123,629Hensel et a1 July 12, 1938 2,255,204 Best Sept. 9, 1941 2,305,172Landgraf Dec. 15, 1942 2,308,584 Best Jan. 19, 1943 2,371,105 LepsoeMar. 6, 1945 2,384,892 Comstock Sept. 18, 1945 2,460,991 Brasse et al.Feb. 8, 1949 2,787,534 Golwynne Apr. 2, 1957 2,861,880 Harmon Nov. 25,1958 2,867,528 Evans et al. Jan. 6, 1959 2,870,485 Jones Jan. 27, 19592,934,787 Hershey et al. May 3, 1960 3,041,672 Lyle July 3, 1962

